Michael Myers - Nick Castle
Michael Myers has been reprised by tons of different actors since all they need is to wear the white mask (which, by the way, is molded off of a mask of William Shatner). Nick Castle plays Myers in the original Halloween film, his imposing stature and emotionless killings making him the perfect villain.
The Pale Man - Doug Jones
The Pale Man is played by Doug Jones, not that you'd be able to tell. He's a special effects actor who specializes in characters such as The Pale Man. Guillermo del Toro features tons of creepy creatures in Pan's Labyrinth, but The Pale Man is easily the most iconic.